what further action can I take if I feel teachers not listening

my 10 year old has had a problem with one boy since he started the school at 4. the head and teachers are aware of the problems but keep telling me that hes from a difficult background etc and my son must learn not to retaliate I feel the school do not punish the other boy and do not take me seriously I have evidence as to how long my sons had the taunting and it is now affecting my sons learning and also his self confidence, please help